It won't let me use Adblock under Firefox 2.0... either alpha 1 or the nightly build (which claims to be "alpha 2"). Is there some technical reason why Adblock doesn't work under Firefox 2.0? Or does it just need to be verified to work and have its "supported versions" field extended?

The problem is that nobody seems to be there to test it in the nightly builds, the developers simply disappeared. Well, Adblock Plus is regularly tested in both 2.0 and 3.0 nightly builds - and works without problems._________________Adblock Plus developer
http://adblockplus.org/